Direct Electrical Heating
Direct Electrical Heating
Direct electrical heating (DEH) is a flow assurance technology developed to
safeguard the well stream through the pipeline to the platform. The pipe is heated
by running alternating current through the steel in the pipe. Nexans pioneered the
development of this technology in cooperation with Statoil and SINTEF more than
20 years ago, and has been the worldwide leader in DEH systems ever since.
DEH is an eco-friendly, chemical-free
system, which greatly reduces the need for
methanol cleansing on the platform. This
allows substantial savings in space and
weight topside. By use of electrical power,
the pipeline is heated to stay above critical
temperature in the event of production
shut-down or low production rates.
DEH allows continuous operation of the
production system and can be turned on
when required.
Proven technology
Direct Electrical Heating has successfully
been installed at a number of fields in the
Norwegian Sea.
The DEH system comprises DEH riser
cable, Armoured Feeder Cable, DEH
Piggyback Cable with Integrated
Protection System (IPS), and associated
mechanical accessories.
up the pipeline. Pipelines are therefore
thermally insulated to ensure flow during
normal production.
pipeline will cool over time. This can
lead to the formation of wax or hydrate
plugs when the temperature drops below
a critical level. This will in effect render
the pipeline useless.
The challenge
Modern oil installations typically have
multiple wells tied back to a single
floating structure, strategically located
near the wells.
The oil/gas exits the well at high
temperature and high pressure, and
must be kept warm in its natural form to
prevent hydrates or wax from clogging
There can be many kilometres between
the well and the platform, leading to
heat loss in the oil/gas. In the event of
production shut-down, the product in the
The Solution
Direct Electrical Heating System
Direct electrical heating (DEH) is a
complete technical solution for heating
pipelines, eliminating the problems
associated with plug formation.
DEH Riser Cable
The Riser Cable supplies power from the
platform down to the sea bed. It can
be designed for one or more systems
and may include hydraulic tubes and
signal cables. The cable is designed,
produced and tested by Nexans.
Armoured Feeder Cable
The Armoured Feeder Cable connects the
DEH Riser Cable to the pipeline and to
the Piggyback Cable. The cable contains
two conductors, one connected to the
pipeline at the platform end and the other
connected to the piggyback cable.
DEH Piggyback Cable
The DEH Piggyback Cable conducts
current from the platform end to the
well. At the well, the Piggyback
Cable is connected to the pipeline
and the current returns to the platform
end through the steel in the pipeline
in parallel with the sea water. The
Piggyback Cable is strapped tightly to
the pipeline to achieve maximum effect
and it has an integrated fibre-optic
system for continuous monitoring along
the entire length.
Integrated Protection System (IPS)
The IPS surrounds the piggyback cable
and protects it from external loads, such
as trawl boards and abrasion.
Background
Pioneer work in DEH development
Nexans began the development of DEH
in partnership with their partners in the
early 1990s.
Our extensive experience in cables
and equipment for the energy industry
provided a basis for our system expertise.
• Through participation in technical
qualification work and in the development
of all systems in operation in the North
Sea, Nexans has developed cables and
equipment for DEH based on the special
demands the technology imposes.
•
The cables in a DEH system are
operated in a different way than a
traditional subsea cable used for power
transmission. The DEH cables are
subject to cyclical operation and high
operating temperatures. This involves
new challenges in terms of the lifetime
of the insulation system. Moreover, the
cable that runs along the pipeline cannot
have metal screening or armouring
because this reduces the efficiency
of the pipe-heating system.
• There are large mechanical loads on
the cable, for example from trawling and
pipe movements.
•
The DEH system produces a certain
electrical current in the water and this
must be taken into account when planning
adjacent equipment, both in terms of
corrosion and effects on signal cables.
• Nexans’ long experience of umbilicaland offshore cables has formed the basis
for more than 15 years of development
focused particularly on DEH. Cables
and components are subject to different
loads during installation and operation
than conventional offshore products. All
design, testing and production is carried
out by Nexans.
References
Project
Year of Installation
Pipeline
Åsgard
2000
10” 13%Cr, 6 off, 6-8.5 km
Huldra
2001
8” 13%Cr, 16 km
Kristin
2004
10” 13%Cr, 6 off, 6-6.7 km
Urd
2005
12.5” Carbon steel with Clad, 9 km
Ormen Lange
2006*
30” Carbon, 2 off, 20 km
Tyrihans
2007/8
16 and 18” Carbon steel with Clad, 42 km
Morvin
2008/9
10.5” 13%Cr, 20 km
Alve
2008
12” Carbon steel with Clad, 16 km
Skarv
2010/11
12” Carbon with Clad, 13 km
Skuld
2012
12/14” Carbon with Clad, 25 km (approx)
More information on www.nexans.no.
Global expert in cables and cabling systems
Nexans Norway AS, Innspurten 9 - Postboks 6450 Etterstad - 0605 Oslo - Telefon: 22 88 61 00 - Telefax: 22 88 61 17 - E-post: landstrom.no@nexans.com
NEXANS NORWAY
ASNorway
forbeholder
seg retten9til- åPostboks
gjøre kabeltekniske
endringer
uten Oslo
varsel,
da våre produkter
stadig utvikling.
Nexans
AS, Innspurten
6450 Etterstad
- NO-0605
- Telephone:
+47 22 er
88under
61 00
E-mail: energymarket.no@nexans.com
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Nexans Norway AS er ledende leverandør av kraft-, tele-, installasjons- og varmekabler i Norge, og er blant
verdens
kontrollkabler
og høyspente
sjøkabler. Selskapet
har hovedkontor
Oslo,
Nexans ledende
Norwayinnen
AS is offshore
a leading
supplier of power,
telecommunications,
installations
and heating i cables
produksjonsanlegg
på
Rognan,
Namsos,
Langhus,
Karmøy
og
i
Halden.
Selskapet
har
ca
1
100
ansatte
og er
in Norway, and is among the world’s leading manufacturers of offshore control cables and high-voltage
organisert
i
tre
divisjoner:
Energi,
Teleog
Installasjonskabel
og
Energinett.
Du
finner
flere
opplysninger
hvis
du
submarine cables. The company’s head office is in Oslo, and it has manufacturing plants at Rognan, Namsos,
klikker
deg
inn
på
www.nexans.no
Langhus, Karmøy and Halden. The company has approx. 1,360 employees.